Marlon Mack attended Booker High School in Sarasota, FL and proved to be a dual-threat on the football field. In his senior year, Marlon Mack rushed for over 1,500 yards and 19 touchdowns on offense and made 100 tackles with 4 interceptions on defense. Marlon Mack received numerous Division-I scholarship offers but eventually decided to commit to the nearby University of South Florida. In just his first game with the USF Bulls, he tied a school record with 275 rushing yards. He would set the USF freshman record with 1,041 rushing yards and found the end zone nine times.
As a sophomore, Marlon Mack started all 12 games for the USF Bulls and rushed for over 1,300 yards with another nine touchdowns. Marlon Mack surpassed Andre Hall's record to be the all-time leading rusher for USF as a junior, compiling nearly 1,200 rushing yards and 15 touchdowns. After a stellar career in Tampa, Marlon Mack declared for the 2017 NFL Draft.
The Indianapolis Colts selected Marlon Mack in the fourth round of the 2017 NFL Draft. He became the first running back to be drafted from the University of South Florida.
He would enter the 2018 NFL Season atop the Indianapolis Colts' depth chart but dealt with injuries in the early part of the season. However, Marlon Mack made a thunderous return with 126 rushing yards and two touchdowns in a 37-5 blowout of the Buffalo Bills. Marlon Mack had 132 rushing yards and another two touchdowns the following week against the Oakland Raiders. He became the first Indianapolis Colts running back since Joseph Addai (2007) to record back-to-back 100-yard rushing games. Marlon Mack finished the 2018 NFL season with 908 rushing yards, 103 receiving yards and 10 total touchdowns.
Marlon Mack also set a franchise postseason record with 148 rushing yards and added a touchdown in the Indianapolis Colts' win over division rival Houston Texans in the 2018 NFL Playoffs.